INNER JOIN multiple tables in C# Dapper library

DapperInnerJoin.cs

        public override async Task<IEnumerable<City>> GetAllAsync()
        {
            var cities = new Dictionary<long, City>();
            //var areas = new Dictionary<long, Area>();
            
            const string sql = 
                @"SELECT c.id, c.name, a.id, a.name FROM cities c
                INNER JOIN city_areas ca ON ca.city_id = c.id
                INNER JOIN areas a ON a.id = ca.area_id";
            
            await Db.QueryAsync<City, Area, City>(sql, (c, a) => {
                // Get City (TryGetValue when Cities should be unique)
                if (!cities.TryGetValue(c.Id, out var city))
                    cities.Add(c.Id, city = c);
                // Get Area
                // We aren't using because Areas isn't unique
                //if (!areas.TryGetValue(a.Id, out var area))
                //{
                    //areas.Add(a.Id, area = a);
                    city.Areas.Add(a);
                //}
                return city;
            });
            return cities.Values.ToArray();
        }